Samson MPL 1204 User Manual

MIXER

SAMSON

®

MPL 1204

Introduction 3

MPL 1204 Features 3

Guided Tour 5

Overview 5
Channels 6
Main Section 8
Rear Panel 11

Connecting The MPL 1204 - General Suggestions 13
Setting Up and Using the MPL 1204 15

Setting the Correct Gain Structure 16

Grounding Techniques 18
Busing, Submixing, and Channel Muting 19
Using Pan 20
Using Equalization 21
Using Aux Sends and Returns 22
Using Inserts 23
PFL/AFL Soloing 24
Applications Notes 25

Using The MPL 1204 As A Recording Mixer 25
Using The MPL 1204 As A Main Live Mixer 26
Using The MPL 1204 As A Keyboard Submixer 27
Linking The MPL 1204 With Other Mixers 28

Appendix A: Block Diagram 29
Specifications 30

Introduction / MPL 1204 Features

Congratulations on purchasing the Samson MPL 1204 four-bus microphone/line
mixer! The MPL 1204 is optimized for use in both live performance and
recording applications, and it can be used wherever there are a number of
microphone or line-level sources that need to mixed down to two or four outputs.
Although the MPL 1204 is designed for easy operation, we suggest you first take
some time to go through these pages so you can fully understand how we’ve
implemented a number of unique features.

In this manual, we’ll provide you with an overview of MPL 1204 features,
followed by a guided tour of its front and rear panels. Then we’ll describe how
the MPL 1204 should be connected to your existing equipment (including wiring
diagrams) and talk about the important topics of gain structure and grounding
techniques. Next, we’ll cover a number of specific MPL 1204 features (such as
busing, submixing, channel muting, as well as using panning, equalization,
auxiliary sends and returns, channel inserts, and PFL/AFL) in detail. Finally,
we’ll wrap things up with a series of applications notes describing a number of
ways to use the MPL 1204 for both recording and live performance, plus
reference Appendices and full specifications. You’ll also find a warranty card
enclosed—please don’t forget to fill it out and mail it so that you can receive
online technical support and so we can send you updated information about
other Samson products in the future.

SPECIAL NOTE: Should your unit ever require servicing, a

Return Authorization

number (RA) is necessary. Without this number, the unit will not be accepted.
Please call Samson at 1-800-372-6766 for a Return Authorization number prior
to shipping your unit. Please retain the original packing materials and, if
possible, return the unit in its original carton and packing materials.

MPL 1204 Features

“MPL” stands for “Mic/Program/Line” and the name describes the broad range of
signals which can be handled by this powerful four-bus mixer. In fact, the
compact design of the MPL 1204 belies an extraordinary versatility. Add
excellent sound quality to the equation, and you’ve got a product which is
equally useful in live performance and for recording (you’ll find descriptions of
each application at the conclusion of this manual). Here are some of the
MPL 1204’s main features:

•Twelve independent channels, with both mic and line inputs for each
channel. This allows you to blend together a variety of source signals,
including dynamic or condenser microphones, keyboards, CD/tape players,
etc. Standard XLR mic connectors (for microphone inputs) and electronically
balanced 1/4" jacks (for line-level inputs) are provided for each channel;
in addition, there is a dedicated stereo CD/Tape input that provides dual
phono (RCA) jacks.

• Four

bus outputs (a “bus” is simply a pathway through which a signal can be
routed) and an electronically balanced main stereo output, with dedicated
front panel control. Any channel input can be routed to either of the two bus
pairs (1/2 or 3/4), and any of the buses can be routed to the Left/Right mix
output with the touch of a button. This flexible design allows you to easily
mute selected channels and/or to create submixes within your main mix.

3

MPL 1204 Features

• Electronically balanced XLR Main stereo outputs as well as an independent
electronically balanced stereo Control Room output (with dedicated level
control) for connection to a power amplifier and studio monitors.

• A phantom power switch enables you to use the MPL 1204 with high-quality
condenser microphones. When turned on, 48 volts of phantom power is
provided to the mic connectors of all twelve input channels.

• Two auxiliary sends and two stereo auxiliary returns (which can be routed to
any of the four buses). Aux send 1 is pre-fader and post-equalizer, while
Aux send 2 is post-fader and post-equalizer.

• Independent 3-band equalization for each channel, with 15 dB of cut or boost
for low (100 Hz) and high (10 kHz) frequencies, and 12 dB of cut or boost for
mid (1 kHz) frequencies.

• Constant level Pan controls for each channel that allow you to precisely
place each input signal in the left-right plane.

• Center detents for all Pan and EQ controls, making it easy to use the
MPL 1204 even in low-light situations such as live performance.

• Selectable

Pre Fade Listen (PFL) or After Fade Listen (AFL) soloing for each
channel. PFL allows headphone monitoring of individual channels, pre-fader
(but post-EQ), while AFL enables headphone monitoring of individual
channels, post-fader and post-EQ. Both types of solo function are
non-mix-destructive in that they do not affect the signal being output
either by the Main, Bus, or Control Room outputs.

• A flexible front panel metering system includes a ten-segment level meter
and allows you to view at a glance the levels of the main Left/Right output,
as well as main power, phantom power, and PFL or AFL status.

• An independent front-panel headphone output with dedicated volume
control for private monitoring of soloed channels.

• Channel inserts for all twelve channels, enabling you to use outboard signal
processors such as equalizers, compressor/ limiters, or noise gates in a
standard “effect loop.”

• Bus inserts allow external signals to be submixed into any or all of the four
buses and also enables linking of multiple mixers.

• The MPL 1204 can be mounted in any standard 19" rack (taking four rack
spaces), making it easy to integrate into any existing system.

• Last but certainly not least, affordability. The MPL 1204 has been designed
from the ground up to provide versatility and excellent sound quality at a
cost-conscious price.

4

Guided Tour - Overview

The following illustration shows an overview of the front panel of the MPL 1204:

5

CH 1 CH 2

TRIM

+4

TRIM

E

M

I

C

N

I

L

+24

-30

-50

+4

+24

HIGH

HIGH

0

+15

-15
MID

MID

0

+12

-12

LOW

LOW

0

+15

-15
AUX 1

AUX 1

PRE

0

+10

∞

AUX 2

AUX 2

POST

0

+10

∞

SOLO

SOLO

ON OFF

ON OFF

MUTE

MUTE

3/4

R

L

PAN

0

+10

∞

LEVEL LEVEL LEVEL LEVEL LEVEL LEVEL LEVEL LEVEL LEVEL LEVEL LEVEL LEVEL

CH 3

+4

+4

TRIM

+24
HIGH

MID

LOW

AUX 1

AUX 2

SOLO

ON OFF

MUTE

3/4

TRIM

E

M

I

C

N

I

L

-30

-50

+4

+24
HIGH

0

+15

-15
MID

0

+12

-12

LOW

0

+15

-15
AUX 1

PRE

0

+10

∞

AUX 2

POST

0

+10

∞

SOLO

ON OFF

MUTE

3/4

R

L

PAN

+10

∞

E

M

I

C

N

I

L

-30

-50

+4

0

+15

-15
0

+12

-12

0

+15

-15

PRE

0

+10

∞

POST

0

+10

∞

3/4

R

L

PAN

+10

∞

CH 5 CH 6 CH 7 CH 8 CH 9 CH 10 CH 11 CH 12

CH 4

+4

+4

+4

+4

+4

+4

TRIM

TRIM

TRIM

TRIM

+24
HIGH

MID

LOW

AUX 1

AUX 2

SOLO

ON OFF

MUTE

3/4

TRIM

E

E

M

I

C

N

N

I

I

L

L

-30

-50

+4

+4

+24
HIGH

0

+15

-15

-15

MID

0

+12

-12

-12

LOW

0

+15

-15

-15

AUX 1

PRE

0

+10

∞

∞

AUX 2

POST

0

+10

∞

∞

SOLO

ON OFF

MUTE

3/4

R

L

L

PAN

+10

∞

∞

E

E

E

M

M

I

I

C

POST

C

N

I

I

L

-30

+24
HIGH

+15

MID

+12

LOW

+15

AUX 1

PRE

0

+10

AUX 2

0

+10

SOLO

ON OFF

MUTE

R

+10

L

-30

-50

+4

+24
HIGH

0

+15

-15

-15

MID

0

+12

-12

-12

LOW

0

+15

-15

-15

AUX 1

PRE

0

+10

∞

∞

AUX 2

POST

0

+10

∞

∞

SOLO

ON OFF

MUTE

3/4

3/4

R

L

PAN

+10

∞

∞

N

I

L

-50

+4

0

-15
0

-12

0

-15

∞

∞

L

PAN

∞

E

M

M

I

I

C

+15

+12

+15

0

+10

POST

0

+10

+10

C

N

I

L

-30

-30

-50

+4

+24
HIGH

0

+15

-15

MID

0

+12

-12

LOW

0

+15

-15

AUX 1

PRE

PRE

0

+10

∞

AUX 2

POST

0

+10

∞

SOLO

ON OFF

MUTE

3/4

R

R

L

PAN

+10

∞

N

-50

+4

0

0

0

L

PAN

+4

TRIM

E

M

I

C

N

I

L

-30

-50

-50

+4

+24
HIGH

0

0

+15

-15

MID

0

0

+12

-12

LOW

0

0

+15

-15

AUX 1

PRE

0

+10

∞

AUX 2

POST

0

+10

∞

SOLO

ON OFF

MUTE

3/4

R

L

PAN

PAN

+10

∞

+4

TRIM

E

M

M

I

C

N

I

L

-30

-50

+4

+24
HIGH

0

+15

-15

MID

0

+12

-12

LOW

0

+15

-15

AUX 1

PRE

0

+10

∞

AUX 2

POST

0

+10

∞

SOLO

ON OFF

MUTE

3/4

R

L

PAN

+10

∞

CHANNELS MAIN SECTION

I

C

+15

+12

+10
POST

+10

AUX RETURNS

STEREO

+4

TRIM

E

M

I

C

N

I

L

MID

LOW

AUX 1

SOLO

ON OFF

MUTE

3/4

∞

-30

-50

+4

AUX RET.1/2

0

MUTE

3/4

+15

-15
0

L
BALANCE

+12

-12

0

∞

AUX RET.3/4

+15

-15

PRE

MUTE

0

3/4

+10

∞

POST

0

L

BALANCE

+10

∞

R

L

∞

PAN

+10

∞

PHONES

-30

+24
HIGH

+15

PRE

0

AUX 2

0

R

+10

0

+10

-20

LEFT

RIGHT

-20

PFL

R

SOLO

0

+10

R

+10
dB

0

0

+10

∞

SAMSON

MPL 1204 MIC MIXER

-9 -6 -3

-15

0+2+4+6

-9 -6 -3

-15

0+2+4+6

POWER

PHANTOM

AFL

PHANTOM METER TAPE
PFL
AFL

∞

MAIN LEVEL

L

+10

CONTROL ROOM

R

BUS 2BUS 1 BUS 3

1-2
3-4

∞

L

BUS 4

+8

+8

11/12

+10

R

+10
dB

0

∞

Guided Tour - Channels

1: Trim (black) - This knob determines the input level of the connected signal.
Continuously adjustable from +4 dB to -50 dB (for mic inputs) or +24 to -30 dB (for line
inputs), the input signal is boosted when the trim is turned clockwise and attenuated when
turned counterclockwise. For information on how to properly set this for each channel, see
the section on page 14 entitled “Setting The Correct Gain Structure.”

2: Equalizer (violet) - These knobs determine the amount of boost or attenuation in each
of three frequency areas (up to 15 dB for low and high frequencies, and up to 12 dB for the
mid frequency). The mid frequency control (centered at 1 kHz) utilizes a resonant (“bell”)
peaking curve, while the high and low frequency controls (centered at 10 kHz and 100 Hz,
respectively) utilize shelving curves. A center detent in each knob (at the “0” position)
indicates no boost or attenuation (that is, flat response). As each knob is turned clockwise
from the “0” position, the frequency area is boosted; as it is turned counterclockwise from
the “0” position, the frequency area is attenuated. For more information on the application
of EQ, see the “Using Equalization” section on page 19 in this manual.

3: Auxiliary sends (blue) - These knobs allow you to route signal to either or both of the
MPL 1204’s two monophonic Auxiliary outputs. These are typically used to create
submixes (for example, a headphone cue mix) and to feed signal from single or multiple
channels to outboard effects devices. At the “0” (2 o’clock) position, the signal is routed
with unity gain (that is, no boost or attenuation). As each knob is turned clockwise from the
“0” position, the signal is boosted; as it is turned counterclockwise from the “0” position, it is
attenuated. Aux send 1 is post-eq but

pre-fade; that is, the level of the signal is determined
solely by its Trim control and its EQ settings (see #1 and #2 above). In contrast,
Aux send 2 is post-eq and

post-fade; that is, the level of the signal is determined by the
channel’s Trim control, its EQ settings, and the position of its Level control. For more
information, see the “Using Aux Sends and Returns” section on page 20 in this manual.

4: Solo On/Off switch - When pressed in, the channel is soloed (in headphones only).
Soloing will be in either PFL (Pre Fade Listen) or AFL (After Fade Listen) mode, depending
upon the setting of the PFL/AFL switch in the MPL 1204 main section. See #7 and #8 on
page 7 and the “PFL/AFL Soloing” section on page 22 in this manual for more information.

5: Mute 3/4 switch - When up, the channel’s signal is routed to the Bus 1/2 faders and
then on to the Bus 1/2 and, optionally, Main and Control Room output jacks (if, as
described in #14 on page 8, the Bus “L/R” switches for those buses is pressed in). When
pressed in, the channel’s signal is instead routed to the Bus 3/4 faders and then on to the
Bus 3/4 and, optionally, Main and Control Room output jacks (if, as described in #14 on
page 8, the Bus “L/R” switches for those buses is pressed in). If you set the Bus 3/4 faders
all the way down (to their “∞” position), this switch can be used for channel muting. See
the “Busing, Submixing and Channel Muting” section on page 17 in this manual for more
information.

6: Pan (green) - This knob allows you to place the input signal anywhere in the left-right
stereo spectrum, while keeping the overall signal level constant. When the knob is placed
at its center (detented) position, the signal is sent equally to both left and right outputs of
the selected bus (depending upon the setting of the channel’s Mute 3/4 switch, as
described in #5 above). When moved left of center, less signal is sent to the right output
and more signal is sent to the left output (making the sound appear left of center) and
when moved right of center, less signal is sent to the left output and more signal is sent to
the right output (making the sound appear right of center). To route a signal hard left or
right, place the pan knob either fully counterclockwise or fully clockwise. For more
information, see the “Using Pan” section on page 18 in this manual.

6

CH 1

TRIM

+24

HIGH

-15

MID

-12

LOW

+4

E

M

I

C

N

I

L

-30

-50

+4

0

+15

0

+12

0

1

2

-15

AUX 1

∞

AUX 2

∞

SOLO

ON OFF

MUTE

3/4

L

∞

PAN

LEVEL

+15

PRE

0

+10

POST

0

+10

R

0

+10

3

4

5

6

7

Guided Tour - Channels

7: Level (white) - This knob (purposely made a little bigger than the others so
you can find it easily in low-light situations) controls the volume of the channel
input. In practice, you will use the Level controls to continuously adjust the
loudnesses of the various signals being blended together by the MPL 1204.
The “0” (2 o’clock) position of the knob indicates unity gain (no level attenuation
or boost). Moving the knob counterclockwise from the “0” position (towards “∞”)
causes the signal to be attenuated (at the very bottom, it is attenuated infinitely—
in other words, there is no sound). Moving it clockwise from the “0” position
(towards “+10”) causes the signal to be boosted by as much as 10 dB.

For best signal-to-noise ratio, all Level controls for channels carrying signal
should generally be kept at or near the “0” position. Channels that are unused
should have their Level controls kept fully counterclockwise at their “∞”
(minimum) level. See the “Setting the Correct Gain Structure” section on
page 14 in this manual for more information.

7

8

Guided Tour - Main Section

1: Auxiliary Return Level (orange) - These knobs determine the input level of
signal arriving via the MPL 1204’s two stereo Auxiliary returns. The “0”
(2 o’clock) position of each knob indicates unity gain (no level attenuation or
boost). Moving each knob counterclockwise from the “0” position (towards “∞”)
causes the signal to be attenuated (at the fully counterclockwise position, it is
attenuated infinitely—in other words, there is no sound). Moving each knob
clockwise from the “0” position (towards “+10”) causes the signal to be boosted
by as much as 10 dB. For information on how to properly set these, see the
sections in this manual entitled “Setting the Correct Gain Structure” and “Using
the Aux Sends and Returns” (pages 14 and 20).

2: Stereo Auxiliary Return Bus switch - These switches determine which of
the two pairs of stereo buses (1/2 or 3/4) the Aux return signal is routed to.
When up, the Return’s signal is routed to the Bus 1/2 faders and then on to the
Bus 1/2 jacks as well as (if the Bus “L/R” switch is pressed in—see #14 on page

8) the Main and Control Room output jacks. When pressed in, the channel’s
signal is instead routed to the Bus 3/4 faders and then on to the Bus 3/4 jacks as
well as (if the Bus “L/R” switch is pressed in) the Main and Control Room output
jacks. If you set the Bus 3/4 faders all the way down (to their “∞” position), this
switch can be used for selective muting of Aux returns. For more information,
see the sections in this manual entitled “Busing, Submixing and Channel Muting”
and “Using the Aux Sends and Returns” (pages 17 and 20).

AUX RETURNS

1

2

3

STEREO

∞

AUX RET.1/2

MUTE

3/4

L

BALANCE

∞

AUX RET.3/4

MUTE

3/4

L
BALANCE

0

+10

R

0

+10

R

SAMSON

MPL 1204 MIC MIXER

-20

-9 -6 -3

-15

LEFT

RIGHT

-20

-9 -6 -3

-15

PFL

PHANTOM METER TAPE

SOLO

PFL
AFL

∞

MAIN LEVEL

L

+10

dB

0

+8

0+2+4+6

+8

0+2+4+6

PHANTOM

AFL POWER

1-2
3-4

+10

R

+10

∞

CONTROL ROOM

R

L

11/12

+10
dB

0

6
7
8

9
10
11
12
13
14

4
5

∞

PHONES

0

+10

∞

BUS 2BUS 1 BUS 3

∞

BUS 4

15

9

Guided Tour - Main Section

3: Stereo Auxiliary Return Balance (brown) - These knobs determine the
relative levels of the left and right input signals connected to the MPL 1204’s two
stereo Auxiliary returns. When the knob is placed at its center (detented)
position, both left and right input signals for that Aux return are at equal strength.
When moved left of center, the left input signal remains at the same strength but
the right input signal is attenuated; when the knob is moved right of center, the
right input signal remains at the same strength but the left input signal is
attenuated. When placed fully counterclockwise, only the left input signal is
heard (panned hard left); when placed fully clockwise, only the right input signal
is heard (panned hard right). These “radical” positions are useful when you are
using a stereo Aux return as two mono returns—see the “Using Aux Sends and
Returns” section on page 20 in this manual for more information.

4: Headphone Level - This knob sets the level of the signal sent to the
headphone jack (see #5 below). WARNING: To avoid possible damage to
connected headphones (or, worse yet, to your ears!), always turn this all the way
off (to the fully counterclockwise “0” position) before plugging in a pair of
headphones—then raise the level

slowly while listening. The Headphone Level

has no effect on the final Main output level or on the Control Room output level.
5: Headphone jack - Connect any standard stereo headphones to this jack

(via a 1/4" TRS plug) for private monitoring of all soloed channels. The built-in
MPL 1204 headphone preamp delivers 120 mw at 33 ohms. For more
information, see the “PFL/AFL Soloing” section on page 22 in this manual.

6: Meter - This ten-segment bar meter shows the continuous output level of
either Bus 1/2 or Bus 3/4, depending upon the setting of the Meter switch
(see # 10 on page 8). For optimum signal-to-noise ratio, try to adjust all channel
levels so that program material is usually at or around 0 VU, with occasional but
not steady excursions to the red “+” segments. See the “Setting the Correct
Gain Structure” section on page 14 in this manual for more information.

7: Status LEDs - These show the status of various conditions within the
MPL 1204. The leftmost LED (labeled “PFL”) lights steadily green when the
MPL 1204 is in PFL mode (see #8 below). The left center LED (labeled “AFL”)
lights steadily red when the MPL 1204 is in AFL mode (see #8 below). The right
center LED lights steadily green when the Phantom Power switch (see #9 below)
is engaged and 48 volts phantom power is being delivered to all XLR mic
connectors. The rightmost LED (labeled “Power”) lights steadily red whenever
the MPL 1204 is powered on.

8: Solo switch - This determines whether the MPL 1204 is in PFL mode (switch
up) or AFL mode (switch pressed in). For more information, see the “PFL/AFL
Soloing” section on page 22 in this manual.

9: Phantom Power switch - When this switch is pressed in, the MPL 1204
delivers 48 volts of phantom power to pins 2 and 3 of all XLR microphone
connectors in all twelve channels. WARNING: Only use this switch with the
MPL 1204 powered down. Before turning phantom power on, be sure to
disconnect all non-microphone signal sources (such as passive direct injection
boxes) from the XLR mic jacks. Although phantom power will have no adverse
affect on connected dynamic microphones, it should be used only when one or
more condenser microphones are connected to the MPL 1204.

Refer to the
owners manual of your microphone to determine whether or not it requires
48 volts phantom power—we cannot assume responsibility if you damage
a mic by incorrectly applying phantom power. If you’re not completely

Guided Tour - Main Section

certain that one or more connected mics require 48 volts phantom power, leave
this switch off (its out position).

10: Meter switch - When out, the ten-segment MPL 1204 meter (see #6 on the
previous page) shows the continuous output level of Bus 1-2; when pressed in,
the meter shows the continuous output level of Bus 3-4.

11: Tape switch - Press this in to route signal connected to the rear panel RCA
jack tape inputs to channels 11 and 12 (the left side is routed to channel 11 and
the right side is routed to channel 12). When this switch is pressed in, any mic
or line input signal connected to channels 11 and 12 is automatically muted.

12: Main Level - This knob determines the final signal level of the rear panel
Main output—you can think of it as being the “master fader.” The 2 o’clock “0”
position of the knob indicates unity gain (no level attenuation or boost). Moving
the knob counterclockwise from the “0” position (towards “∞”) causes the signal
to be attenuated (at the very bottom, it is attenuated infinitely—in other words,
there is no sound). Moving it clockwise from the “0” position (towards “+10”)
causes the signal to be boosted by up to 10 dB. For more information, see the
“Setting The Correct Gain Structure” section on page 14 in this manual.

13: Control Room Level - This knob determines the signal level of the rear
panel Control Room output, allowing independent monitoring of the Main output
signal. The 2 o’clock “0” position of the knob indicates unity gain (no level
attenuation or boost). Moving the knob counterclockwise from the “0” position
(towards “∞”) causes the signal to be attenuated (at the very bottom, it is
attenuated infinitely—in other words, there is no sound). Moving it clockwise
from the “0” position (towards “+10”) causes the signal to be boosted by up to
10 dB.

14: Bus L/R switches - These switches allow you to route the output from the
four buses to the Main left/right output jacks and Control Room left/right output
jacks on the rear panel (see #10 and #11 on page 10). When this switch is up,
the signal from that bus is not routed to the main outputs and instead terminates
at its Bus out jack (see #12 on page 10). When pressed in, the signal from that
bus is routed to the Main and Control Room outputs (buses 1 and 3 are routed to
the left Main and Control Room output jacks and buses 2 and 4 are routed to the
right Main and Control Room output jacks) as well as to its Bus out jack.
For more information, see the “Busing, Submixing and Channel Muting” section
on page 17 in this manual.

15: Bus Faders (white with blue line) - These linear sliders determine the
relative level of the four bus outputs. The “0” position of each fader indicates
unity gain (no level boost or attenuation). Moving the fader below this position
(towards the “∞” position) causes the signal to be attenuated (at the very bottom,
it is attenuated infinitely—in other words, there is no sound). Moving it above
this position (towards the “+10 dB” position) causes the signal to be boosted by
up to 10 dB. For best signal-to-noise ratio, all Bus faders should generally be
kept at or near the 0 level. For more information, see the “Setting The Correct
Gain Structure” and the “Busing, Submixing and Channel Muting” sections on
pages 14 and 17 in this manual.

10

Guided Tour - Rear Panel

1: Power on-off switch - As you may have guessed, this is what you use to turn the
MPL 1204 on and off. To avoid potential damage to your speakers, turn the MPL 1204
on before you turn on any connected power amps—and turn it off after the power amps
are turned off.

2: Fuse - Contains a 1 amp, 250 volt fuse for 115 volt operation or a 0.5 amp, 250 volt
fuse for 230 volt operation.

3: AC input - Connect the supplied standard 3-pin “IEC” plug here.
4: Mic inputs (1 - 12) - Use these electronically balanced XLR jacks to connect

microphones to the MPL 1204. These are intended to accept signal from low-level,
low-impedance mics but can also be used for signal from other sources (such as direct
injection boxes) if the channel’s Trim control (see #1 on page 4) is turned down.
WARNING: Do not connect a channel’s microphone input if you already have something
connected to its line input (see #5 below); all channels are designed to accept only one
source or the other.

5: Line inputs (1 - 12) - Use these electronically balanced 1/4" jacks to connect
line-level sources such as synthesizers, drum machines, CD players, tape decks, or
effects processors to any of the MPL 1204’s twelve channels. Use balanced three­conductor cabling and Tip/Ring/Sleeve (TRS) plugs wherever possible (unbalanced
two-conductor plugs can also be inserted into these inputs, but you’ll get better signal
quality and less outside noise and hum if you use balanced lines). The “Connecting the
MPL 1204” section on page 11 in this manual provides more information on how best to
use channel inputs.

WARNING: Do not connect a channel’s line input if you already
have something connected to its microphone input (see #4 above); all channels are
designed to accept only one source or the other.

6: Channel Inserts (1 - 12) - Use these to insert an external effects processor (such as
outboard equalizer, compressor/limiter or noise gate) into any of the MPL 1204’s
channels in an “effects loop” configuration. These jacks accept 1/4" TRS plugs, with
the ring carrying the send signal and the tip carrying the return signal. Normally, this
will be connected to a Y-cord; see the “Connecting The MPL 1204” section on page 12
in this manual for more information and a wiring diagram.

11

7

9

4

MPL 1204 12 CHANNEL MIC MIXER

TRS

POWER

1

FUSE

1A/250V[115V]

0.5A/250V[230V]

2

3

STEREO INPUT
TIP = LEFT

RING = RIGHT
SLEEVE = COM

ON

BALANCED
TIP = HI
RING = LO

OFF

SLEEVE = COM

TRS INSERT
UNBALANCED
TIP = RETURN
RING = SEND
SLEEVE = COM

BALANCED

RISQUE DE CHOC ELECTRIQUE

DO NOT EXPOSE THIS EQUIPMENT

TO RAIN OR MOISTURE.

POWER
RATING

~AC INPUT
115V/230V

50/60Hz, 25W

TRS

XLR

3 = LO
2 = HI
1 = COM

AVIS;

NE PAS OUVRIR

115V/230 - 50/60 Hz 25W

CAUTION

RISK OF ELECTRIC SHOCK

DO NOT OPEN

2

1

3

12

UNBALANCED 10KΩ +4dBu

UNBALANCED <75Ω +4dBu

!

2

1

3

11

AUX RETURNS

STEREO INPUTS

2

AUX SENDS

S / N

8

2

2

1

3

10987654321

TAPE IN

1/23/4

UNBALANCED

10KΩ -10dBu

L/11

R/12

1

RIGHT

2

BALANCED <75Ω +4dBu

LEFT

2

1

3

3

MAIN

10

2

2

2

1

1

3

3

MICROPHONE INPUTS BALANCED +4dBu TO -50dBu

12121111101099887766554

RIGHT LEFT

1

CONTROL ROOM

BALANCED <75Ω +4dBu

1

3

LINE INPUTS BALANCED +24dBu TO -30dBu

CHANNEL INSERTS TIP RETURN -RING SEND -SLEEVE GND

4123

11

2

1

3

3

BUS OUTPUTS

UNBALANCED 75Ω +4dBu

12

1

SAMSON

2

2

2

1

3

1

3

4

4123

BUS INSERTS

UNBALANCED 75Ω +4dBu

MIXER LINKING

3

3

2

1

3

1

3

1

2

1

2

5

6

13

12

Guided Tour - Rear Panel

7: Aux Returns (1/2, 3/4) - These unbalanced 1/4" TRS inputs allow you to
route signal from external devices such as effects processors to either of the two
stereo Aux Returns. These jacks accept 1/4" TRS plugs, with the tip carrying
the left signal and the ring carrying the right signal (sleeve is common ground).
See the “Using Aux Sends and Returns” section on page 20 in this manual for
more information.

8: Aux Sends (1, 2) - These unbalanced 1/4" outputs allow you to route signal
from either of the two discrete Aux Sends to external devices such as effects
processors. All four MPL 1204 Aux sends are post-fade. See the “Using Aux
Sends and Returns” section on page 20 in this manual for more information.

9: Tape/CD inputs (L, R) - Use this set of dual RCA jacks to connect the
outputs of a tape or CD player to the MPL 1204. When the “Tape” switch
(see #11 on page 8) is pressed in, signal connected here is routed to channels
11 and 12 (the left side is routed to channel 11 and the right side is routed to
channel 12), with any mic and line input signal connected to channels 11 and 12
automatically muted.

10: Main outputs (L, R) - These are the MPL 1204’s main outputs. In live
performance applications, you’ll usually use these to connect the MPL 1204 to
a power amp and speakers; in recording applications, these will normally be
connected to the inputs of a two-track recorder. The Main out XLR jacks are
electronically balanced, so you should use balanced three-conductor cabling
wherever possible for optimum signal quality and reduced outside noise and
hum. See the “Connecting the MPL 1204” section on page 11 in this manual for
more information.

11: Control Room outputs (L, R) - In recording applications, these will
normally be connected to a power amplifier and loudspeakers. The Control
Room out jacks are electronically balanced, so you should use balanced
three-conductor cabling and 1/4" TRS plugs wherever possible (unbalanced
two-conductor plugs can also be inserted into these outputs, but you’ll get better
signal quality and less outside noise and hum if you use balanced lines). See
the “Connecting the MPL 1204” section on page 11 in this manual for more
information.

12: Bus outputs (1 - 4) - These unbalanced outputs allow you to route signal
from each of the four discrete buses to external devices such as a multitrack
digital or analog tape recorder. The signal is post-bus fader but pre-Main
control. See the “Busing, Submixing, and Channel Muting” section on page 17
in this manual for more information.

13: Bus Inserts (1 - 4) - Use these to insert an external effects processor
(such as outboard equalizer, compressor/limiter or noise gate) into any of the
MPL 1204’s four buses in an “effects loop” configuration. This enables you to
process a group of signals simultaneously (such as a drum submix being sent to
a single track of a tape recorder) at unity gain. These jacks accept 1/4" TRS
plugs, with the ring carrying the send signal and the tip carrying the return
signal. Normally, this will be connected to a Y-cord; see the “Connecting The
MPL 1204” section on page 12 in this manual for more information and a wiring
diagram. Bus inserts can also be used to link multiple MPL 1204s or to bring the
output from another mixer into the MPL 1204 without taking up channel line
inputs. See the “Using Inserts” section on page 21 and the “Linking the
MPL 1204” Application on page 26 in this manual for more information.

13

Connecting The MPL 1204 - General Suggestions

The actual connections you’ll make to and from the MPL 1204 will vary
according to the environment you use it in and the particular equipment you
have. In the “MPL 1204 Applications” sections at the rear of this manual,
you’ll find some suggested setups. Here are a few basic rules concerning
MPL 1204 connections that will apply in most situations:

• In general, it’s best to make all connections with the MPL 1204 and any
connected power amplifiers turned off. If you must make connections with
the power on, make sure that the Main and Control Room Level knobs are
completely counterclockwise and that all four bus faders are completely
down (at their “∞” position). Whenever powering down, bring the Main and
Control Room Level knobs completely counterclockwise and set all four bus
faders completely down, turning off the main power amps

first. Wait a few
seconds for their power supplies to discharge and then turn off all connected
equipment, turning the MPL 1204 off

last.

• Try to use balanced connectors and cabling wherever possible. These kind
of connections do a better job of rejecting extraneous noise and hum and
generally provide a cleaner signal. Although the MPL 1204 will accept
unbalanced connectors throughout, it specifically provides electronically
balanced inputs for all mic and line inputs and for its Main and Control Room
outputs. The wiring diagram below shows how 1/4" TRS (Tip/Ring/Sleeve)
connectors should be wired for use with line-level inputs and Control Room
outputs:

XLR connectors for mic-level inputs and the Main outputs should be wired as
follows:

Unbalanced cables use standard 1/4" phone connectors, wired as follows:

• Make one connection at a time and then monitor the incoming signal. If you

hear a distinct hum or buzz, you may have a grounding problem with that
particular device. See the “Grounding Techniques” section on page 16
in this manual for information on how to avoid grounding problems.

3

SIGNAL

T

TO MIC
OR POWER
AMPLIFIER

SLEEVE

TIP

RING

­1 GROUND
2 + SIGNAL

TIP +
GROUND
RING -

+ SIGNAL

+ SIGNAL

GROUND

GROUND

14

• NEVER connect a microphone and line level input to the same channel
simultaneously—use one or the other. You can have some channels
connected to microphones and others to line level signals (for example, you
might want to plug mics into channels 1 - 4 and line level signals into the
remaining channels)—just don’t have both kinds of inputs connected to the
same channel.

• There are two “hidden” (or at least not so obvious) stereo inputs to the

MPL 1204; these are the Auxiliary returns. Use these whenever you want
to bring in stereo signals that will not need to be equalized.

• Channel and bus insert cables (sometimes called “Y-cords”) should
terminate in standard 1/4" TRS jacks (ring to send and tip to return), wired
as follows:

• The MPL 1204 Aux return jacks are unbalanced stereo inputs, with the tip
carrying the left input signal and the ring carrying the right input signal
(with the sleeve carrying common ground), as shown below. Insertion of
a monophonic 1/4" jack into an Aux return will result in the incoming signal
being automatically routed to the left input only (and therefore panned hard
left).

Connecting The MPL 1204 - General Suggestions

TIP (RETURN)

RING (SEND)

SLEEVE (GROUND)

TIP (LEFT SIGNAL)

RING (RIGHT SIGNAL)

SLEEVE (COMMON GROUND)

15

Setting up your MPL 1204 is a simple procedure which takes only a few minutes:

1. Remove all packing materials (save them in case of need for future service)
and decide where the unit is to be physically placed—it can be mounted in any
standard 19" rack, requiring four rack spaces, or used on a tabletop.

2. Before even plugging the unit into an AC socket, begin by connecting the
MPL 1204 Main or Control Room outputs into a power amp and the amp into
loudspeakers (you’ll usually connect the Main output to a power amp in live
performance environments and the Control Room output to a power amp when
using the MPL 1204 for recording). It is never a good idea to power up any
amplifier that is not connected to loudspeakers.

3. Next, make the signal input connections to the mic or line inputs of the
various channels.

WARNING: Do not connect a channel’s line input if you
already have something connected to its microphone input, or vice versa; each
channel is designed to accept only one source or the other.

4. Set all channel Trim controls fully counterclockwise (to their “+4” setting) and
turn all channel Level controls fully counterclockwise (to their “∞” setting). Then
bring all four bus faders completely down (to their “∞” setting), and set the Main
and Control Room Level controls fully counterclockwise (to their “∞” setting).
Finally, connect the IEC main power cord and plug the MPL 1204 into any
grounded AC socket.

5. Turn on the rear panel Power switch—the “Power” LED in the main section
will light up.

Setting Up and Using The MPL 1204

RIGHT

2

1

3

BALANCED <75Ω +4dBu

SAMSON

RIGHT LEFT

LEFT

2

MAIN

SERVO - 240

1

3

CONTROL ROOM

BALANCED <75Ω +4dBu

SAMSON

SERVO - 240

16

You’re now ready to establish the correct gain structure—the key to getting the
best performance from the MPL 1204, or from any mixer, for that matter. This is
a simple procedure that ensures optimum input and output levels so that no
unnecessary noise (caused by too low a signal) or overload distortion (caused by
too high a signal) is created. Here’s a step-by-step description of how to do so:

a. With all connections made (as described above) but with

the power amplifier

and MPL 1204 off, start by setting the power amplifier volume to minimum.

On the MPL 1204, set all channel Trim knobs to their fully counterclockwise (+4)
position and turn all channel Level controls fully counterclockwise (to their “∞”
position). Set all channel EQ and Pan knobs to their center detent “0” positions.

b. Make sure the Mute switch for all channels is set to the out (unmuted)
position check that the Meter 1-2 / 3-4 switch (in the main section) is set to its out
(1-2) position. This ensures that all channels are routing signal solely to buses 1
and 2 and that the meter will display the bus 1-2 output.

c. If the Main output jacks are connected to a power amplifer and loudspeakers
(as described in #2 on page 13), set the Main Level knob to its 2 o’clock “0”
position. If the Control Room output jacks are connected to a power amplifer
and loudspeakers (as described in #2 on page 13), set the Control Room Level
knob to its 2 o’clock “0” position.

d. Set all channel Aux send knobs and both Aux return Level knobs to their fully
counterclockwise (“∞”) position. Set both Aux return Balance knobs to their
center detent “0” positions.

e. Turn on all devices connected to channel line inputs and Aux returns and set
their output level controls to unity gain or, if there is no unity gain indicated on
their output control, to maximum. If you’ve got outboard effects processors
connected to Aux returns, make sure they are sending completely “wet”
(processed) signal, with no “dry” (unprocessed) signal mixed in. If condenser
microphones are connected to the MPL 1204, turn on the Phantom switch.*

f. Set the bus 1 and bus 2 faders at their “0” (unity gain) position and turn on the
MPL 1204’s rear-panel Power switch—the Power LED in the main section will
light up. Finally, turn on your power amplifier.

g. Play an instrument connected to one of the MPL 1204’s line inputs** and,
while doing so, slowly raise the corresponding channel Level control to the
2 o’clock “0” position. You should see the MPL 1204 meters begin to move.
While watching the meters, adjust the Trim control for that channel so that the “0”
segment lights frequently, with only occasional excursions into the “+” segments.
If the signal seems too hot even with the input channel trim all the way at its
minimum (+4) setting, you may need to lower the output level of the instrument,
though this will rarely occur. Conversely, if the signal is too low even with the
input channel trim all the way up, something's definitely wrong: in all likelihood,
the connecting audio cable is faulty.

* CAUTION: Before turning phantom power on, be sure to verify that all
connected mic(s) and/or active DI boxes require 48 volts. Also, disconnect all
other signal sources (such as passive DI boxes) from the XLR mic jacks.

** If you’re using an instrument such as electric guitar or bass, we recommend
that you connect it to the MPL 1204 with a direct injection box to ensure correct
impedance.

Setting the Correct Gain Structure

17

Setting the Correct Gain Structure

h. Once you’ve set the optimum level in step (g) above, continue playing the
instrument and slowly raise the level of your power amplifier until you reach the
desired listening level. Repeat step (g) above for each instrument connected to
the MPL 1204 channel line inputs.

i. The procedure for setting optimum microphone levels is virtually identical; sing
or speak into each mic at the level you expect to use in performance while slowly
raising the Level control for that channel to its “0” position. Then adjust the Trim
control for that channel while watching the segment meter. You should expect
that mic-level inputs will require rather more in the way of Trim boost than
line-level inputs.

j. If you have any outboard signal processors connected to the Aux send and
return jacks on the rear panel, follow this step. Because outboard effects
processors can sometimes be quite noisy, it’s particularly important to maximize
the amount of signal being sent to them via the MPL 1204 Aux sends. The idea
is to drive these devices as hot as possible (short of overloading them) and then
to use the corresponding Aux return level to carefully adjust the amount of
processed signal being blended with the dry signal. To set optimum Aux send
levels, use a channel that has already had its gain structure adjusted in step (g)
or (i) above. Turn both Aux send knobs for that channel to their “0” (unity gain)
position. Then play the instrument (or sing into the microphone) connected to
that channel. Adjust the input levels of connected outboard effects processors
so that their meter shows incoming signal normally in the 0 vu range (with only
occasional higher excursions). Finally, optimize the Aux return levels: While
continuing to play your instrument (or continuing to sing into the microphone),
slowly raise each Aux return level control until you hear the desired amount of
processed signal added to the dry signal. Adjust the Aux return Balance controls
as required in order to set the relative levels of the signal arriving at the left and
right Aux return inputs. For more information, see the “Using Aux Sends and
Returns” section on page x in this manual.

k. At this point, if you want to route any channel or Aux return signal(s) to any of
the four bus outputs at optimum level, simply set the channel’s “Mute 3/4” or
Aux return’s Bus switch correctly and raise the corresponding bus fader to its “0”
(unity gain) position.

l. The gain structure is now correctly set—you’ve optimized the level of all
signals coming into and out of the MPL 1204, and the end result will be minimum
noise and distortion and maximum clean sound. You’ll now find that the majority
of your mixes can be accomplished with the Main or Control Room Level knobs
and with most channel Level controls at or near their 2 o’clock “0” (unity gain)
position. If you need to make adjustments to the overall level, use the level
control of your power amplifier.

If you encounter difficulty with any aspect of setting up or using your MPL 1204,
you can call Samson Technical Support (1-800-372-6766) between 9 AM and
5 PM EST.

18

Grounding Techniques

Hum and buzz are the biggest enemies you face when interconnecting a large number of different pieces of
equipment to a central audio mixer. This is because each piece of equipment may operate at a marginally different
voltage (this difference is called potential) and, when two devices at slightly different potential are physically
connected with audio cabling, the end result can be nasty, extraneous noise (mind you, connecting two devices at
very different potential can result in a major electrical shock!).

However, there are several steps you can take to avoid grounding problems. First, assuming you have an isolated
electrical circuit that can handle the electrical demands of your mixer and all connected audio equipment (these
needs will usually be modest), you should always plug your mixer and all connected equipment into the same
circuit. If possible, nothing else but this equipment should be connected to that circuit. If you can’t do this, at least
avoid plugging your mixer and audio equipment into the same circuit that is already powering things like heavy
machinery, air conditioners, heaters, refrigerators, washing machines, neon signs or fluorescent light fixtures.
One particular culprit that will almost certainly create problems is the standard light dimmer (the kind that uses
silicon controlled rectifiers). Where low-level lighting is desired, use incandescent fixtures with autotransformer-type
dimmers (sometimes called

Variacs) instead—these cost considerably more than the standard dimmer you’ll find at

your local hardware store, but are well worth the extra expense.
Three-prong plugs (such as the one used by the MPL 1204) should always be used as is; don’t use adapters to lift

the ground (unless you’re using a “star ground network”—see below). If you hear hum or buzz from a device that
uses a two-prong plug (or an external two-prong AC/DC adapter), you can try reversing the plug in the socket.
If that doesn’t work, you may need to physically ground that device’s chassis by connecting a wire (called a

strap)
from it to a grounded piece of metal. Some pieces of equipment have a screw-type ground post to which the strap
can be connected; if not, you can attach some kind of metallic binding post to the case itself. If you are using
rack-mounted audio devices and are experiencing hum or buzz, there’s a simple test to determine the source of the
problem: while keeping all devices powered on and connected with audio cabling, physically remove each device,
one by one, from the rack. If the hum disappears when a particular device is removed, you’ll know that device is
probably the culprit.

We also recommend that you use balanced audio cabling and connectors wherever possible. The MPL 1204
provides electronically balanced inputs for all line channel inputs and for its Main outputs. The wiring diagram in the
“Connecting The MPL 1204” section of this manual (page 11) shows how 1/4" TRS (Tip/Ring/Sleeve) and XLR
connectors should be wired for use with these inputs and outputs.

In addition, you can minimize possible interference by planning your audio, electrical, and computer cable runs so
that they are as far apart from one another as possible and so they don’t run parallel to one another. If they have to
cross, try to ensure that they do so at a 90° angle (that is, perpendicular to one another). In particular, try to keep
audio cabling away from external AC/DC adapters.

If you’re using the MPL 1204 in a fixed location such as a recording studio, you may want to invest the time and
money into creating a

star ground network. This is by far the best technique for avoiding grounding problems.
It involves using a formidable ground source such as a cold water pipe or a copper spike driven into the earth.
A thick grounding cable is connected to that source and then brought to a central distribution point; from there,
individual cables are connected to each piece of equipment. This setup also requires that you lift the ground plug of
all three-prong AC connectors, so there is the possibility of danger if it is done incorrectly. We strongly recommend
that you contract with a qualified professional to carry out this or any kind of electrical work.

Another, less common problem you may encounter is that of

oscillation (a ringing tone), which, apart from being
annoying, is potentially dangerous to your speakers. This is generally caused either by poor outside wiring or by
returning a signal out of phase (most commonly from an outboard signal processor). If audible oscillation occurs, try
isolating each input signal by turning down all other inputs. If one signal alone is causing the problem, you should
be able to eliminate the oscillation by reversing that signal’s phase (many signal processors have a switch that
allows you to do this).

19

Busing, Submixing and Channel Muting

As we’ve seen, the MPL 1204 uses a system of four buses—pathways through
which signal can be routed. The four MPL 1204 bus faders control the overall
level of the signal being output through the four buses. When the “L/R” switches
above each bus fader are pressed in, the signal from that bus is also routed to
the Main and Control Room outputs. In this case, buses 1 and 3 are
automatically routed to the left side of the Main and Control Room outputs and
buses 2 and 4 are automatically routed to the right side of the Main and Control
Room outputs. This four-bus system (which can eventually mix down to a single
stereo output) gives you a great deal of flexibility in terms of signal flow.

For example, you may want to connect the MPL 1204 to a four-track cassette or
open-reel tape recorder. One good way to do this is to route each of the four
individual bus outputs to a tape input, and to bring each of the four tape outputs
back to individual channels. With this setup, to record onto track 1, you’d route
one or more instrument or microphone channels to bus 1 (via the channel “Mute
3/4” switch); to record onto track 3, you’d route them to bus 3, etc. To connect
the MPL 1204 to an eight-track digital recorder (such as the Alesis ADAT™ or
Tascam DA88™ system), simply use signal splitters or patchbay mults to
combine the signal from buses so that bus 1 is routed to tape inputs 1 and 5;
bus 2 to tape inputs 2 and 6; bus 3 to tape inputs 3 and 7; and bus 4 to tape
inputs 4 and 8. See the “Applications” section on page 23 in this manual for
more information on using the MPL 1204 as a recording mixer.

Another important plus is that you can use each bus to set up a

submix within
your overall mix. For example, let’s suppose that you’re using the MPL 1204 to
do live sound and you have eight microphones on the drum kit—separate mics
for the bass and snare drums as well as for the hi-hat, another mic for each of
three tom-toms, and an overhead pair for picking up cymbals. To get all this
signal into the MPL 1204, you’re going to have to use eight mono channels.
During a sound check, you’ll usually start with the drums, working to get the
blend of the eight different drum mics just right. After that’s done, the next step
is typically to start bringing in the other instruments. During the gig, however,
you may need to raise or lower the overall level of the drums, but you surely
won’t want to upset the blend you so carefully set up. This won’t be easy to do if
you have to move eight faders at once! The solution is to use the busing system
provided by the MPL 1204—route the eight drum channels to one pair of buses
and all other instruments to the other pair. Now you can adjust the overall level
of the entire drum mix by moving just two bus faders!

You can also use the MPL 1204 bus switches to

mute particular channels (that
is, remove them temporarily from the overall mix without having to change their
fader position). To do this, keep bus faders 3 and 4 down at their “∞” position
(no signal) and use buses 1 and 2 for your overall mix. Then, to mute a signal,
all you have to do is press that channel’s “Mute 3/4” switch; the signal will be
rerouted to buses 3 and 4 (which are off) and will be removed from the mix you
hear. To restore the signal (that is,

unmute it), all you have to do is press that
channel’s “Mute 3/4” switch again—since its fader hasn’t been moved, the sound
will come back at the same level as before.

+10
dB

+10
dB

0

∞

0

∞

4123

BUS INSERTS

UNBALANCED 75Ω +4dBu

MIXER LINKING

+10

dB

0

∞

+10
dB

0

∞

MUTE

3/4

20

Using Pan

The final Main output of the MPL 1204 is stereo—that is, there are two discrete
Main output jacks (and two discrete Control Room output jacks), labeled “left”
and “right,” which will normally be routed to two discrete speakers.* Because of
this, you will usually be working with a stereo field that ranges from hard left to
hard right. The MPL 1204 provides twelve monophonic input channels, each
with its own dedicated Pan control. The Pan circuitry in the MPL 1204 always
keeps the overall level constant, regardless of pan position. Here’s how it works:
When the Pan knob is placed at its center (detented) position, signal is sent
equally to both left and right outputs of the selected bus (depending upon the
setting of the channel’s Mute 3/4 switch, as described in #5 on page x). When
moved left of center, less signal is sent to the right output and more signal is sent
to the left output (making the sound appear left of center) and when moved right
of center, less signal is sent to the left output and more signal is sent to the right
output (making the sound appear right of center). To route a signal hard left or
right, place the pan knob either fully counterclockwise or fully clockwise.

You can use stereo panning creatively in a variety of ways: For example, you
might want to have guitars coming from one speaker and keyboards from
another, or you might use panning to “spread” the signal from a piano miked with
two microphones—one over the bass notes (panned left) and the other over the
treble notes (panned right). In live performance, you may want to resist the
temptation to pan anything completely hard left or right, since some members of
the audience not seated in the center of the venue may miss some signal
altogether. In these circumstances, you’re best to use modest panning, with
signals routed no further than the 9 o’clock and 3 o’clock positions.

* You can, of course, also use the MPL 1204 monophonically—simply route the
same signal to both the left and right outputs.

L

R

PAN

21

Using Equalization

One of the most exciting aspects of using a mixer such as the MPL 1204 is the
ability to shape a sound, using a process called equalization. But there are few
areas of sound engineering more misunderstood than equalization, and, just as
good EQ can really help a sound, bad EQ can really hurt it, so read on...

Every naturally occurring sound consists of a broad range of pitches, or
frequencies, combined together in a unique way. This blend is what gives every
sound its distinctive tonal color. The EQ section in a mixer allows you to alter a
sound by boosting or attenuating specific frequency areas. The MPL 1204
provides independent three-band equalization controls for each of its channels
(the same equalization is applied to both the odd-numbered [left] input and the
even-numbered [right] input). Each EQ knob is labeled with the maximum
amount of cut or boost provided (± 15 dB in the case of Low and High
frequencies, and ±12 dB in the case of the Mid frequency). The Mid frequency
control utilizes a resonant (“bell”) peaking curve, while the Low and High
frequency controls utilize

shelving curves. This means that, in the case of the
Mid EQ control, frequencies around 1 kHz are affected; in the case of the Low
EQ control, frequencies around or below 100 Hz are affected; and, in the case of
the High EQ control, frequencies around or above 10 kHz are affected. We
provided these particular frequency areas because they have maximum impact
on musical signals—that’s why they are sometimes known as “sweet spots.”

When an EQ knob is in its center detented position (“0”), it is having no effect.
When it is moved right of center, the selected frequency area is being boosted;
when it is moved left of center, the frequency area is being attenuated.

In most instances, the best way to approach equalization is to think in terms of
which frequency areas you need to attenuate, as opposed to which ones you
need to boost (boosting a frequency area also has the effect of boosting the
overall signal; too much EQ boost can actually cause overload). Be aware of the
phenomenon of

masking, where loud sounds in one frequency range obscure
softer sounds in the same range; by cutting EQ “notches” in a loud signal, you
can actually make room for a softer one to shine through. And try not to think of
EQ as a miracle worker—no amount of equalization can put a singer in tune or
remove the distortion from an overloaded input signal! The key is to get the
signal right in the first place, by using correct gain structure and mic placement.

Although the specific EQ you will apply to a signal is very much a matter of
personal taste, here are a few general suggestions: Boosting the low frequency
of instruments such as bass drums or bass guitar will add warmth and make the
sound “fatter”; conversely, you may want to attenuate the low frequency
component of instruments such as cymbals, high-hats, and shakers so as to
“thin” them out. Boosting Mid frequencies can be used to help bring out vocals
or guitars, while attenuating them can help to reduce “boxiness.” Be careful not
to boost high frequencies too much or you risk adding hiss to the signal, though
just a touch can help add “shimmer” to an acoustic guitar, ride cymbal, or
high-hat. Finally, because the MPL 1204 High and Low EQ utilize shelving
curves, attenuated High settings can be used to reduce hiss (which is
composed almost exclusively of high frequencies) or attenuated Low frequencies
can be used to reduce rumble (which is composed almost exclusively of low
frequencies).

HIGH

MID

LOW

-15

-12

-15

0

+15

0

+12

0

+15

22

Using Aux Sends and Returns

The MPL 1204’s two Auxiliary sends allow you to combine the signal from
multiple channels and send the resulting mix to external devices such as effects
processors. When an Aux send knob is at its 2 o’clock “0” position, the signal is
routed with unity gain (that is, no boost or attenuation). As it is turned clockwise
from the 0 position, the signal is boosted; as it is turned counterclockwise from
the 0 position, it is attenuated. Aux send 1 is

pre-fade (but post-eq); that is, the
level of the signal is determined solely by the channel’s Trim control and its EQ
settings. In contrast, Aux send 2 is

post-fade (and post-eq); that is, the level of
the signal is affected by the channel’s Trim control, equalizer settings, and Level
control.

The MPL 1204 also provides two stereo Auxiliary returns. These allow you to
return signal from outboard devices in stereo pairs. Each of the stereo Auxiliary
returns is somewhat similar to a stereo channel, except that a signal being
brought into to a channel can be equalized if necessary and optionally sent on to
other outboard devices (via Aux sends or channel inserts). In practice, you’ll
probably want to use the Auxiliary returns to bring in signal from connected
effects processors. If the effects processors have stereo outputs, they should be
connected to both the left and right Aux return inputs so that their stereo integrity
is retained. If they have mono outputs, you can route them to either the left or
right inputs and then use the Aux return Balance control to adjust the relative
level of each paired signal. In this way, you can actually connect up to four
monophonic devices to the MPL 1204’s Aux return section.

When an Aux return Balance knob is placed at its center (detented) position,
both the left and right signals are at equal strength. When moved left of center,
the left input signal remains the same but the right input signal is attenuated;
when the knob is moved right of center, the right input signal remains the same
but the left input signal is attenuated. When placed fully counterclockwise, only
the left input is heard (panned hard left); when placed fully clockwise, only the
right input is heard (panned hard right).

Signal arriving at the left Aux return input is automatically panned hard left and
signal arriving at the right input is automatically panned hard right. The
MPL 1204 Aux return jacks are unbalanced stereo inputs, with the tip carrying
the left input signal and the ring carrying the right input signal (the sleeve carries
common ground), as shown in the wiring diagram on page 12 of this manual.
Insertion of a monophonic 1/4" jack into an Aux return will result in the incoming
signal being automatically routed to the left input only (and therefore panned
hard left).

The signal arriving at each of the two stereo Aux returns can be routed to either
of the two bus pairs (1/2 or 3/4) with the use of the associated Aux Return bus
switch (as described in #2 on page 6). The signal can then be routed to the
Master and Control Room outputs by pressing in the associated bus L/R switch
(as described in #14 on page 8). Note that Aux Returns cannot be soloed and
so cannot be monitored over headphones.

AUX 1

∞

AUX 2

∞

AUX RETURNS

STEREO

∞

AUX RET.1/2

MUTE

3/4

PRE

0

+10

POST

0

+10

0

+10

L
BALANCE

∞

AUX RET.3/4

MUTE

3/4

L
BALANCE

R

0

+10

R

23

Using Inserts

In addition to using Auxiliary sends and returns to access outboard devices, the
MPL 1204 also provides channel inserts for each of its twelve input channels.
These should be used when you want to affect just one input signal, as opposed
to signal from several inputs—most often, this will be for dynamic processing
purposes (such as outboard equalization, compression/limiting, or noise gating).
You can also use the channel insert sends as post-eq (but pre-fade)

direct

outputs, if you need to route a single monophonic signal to an external device

such as a tape deck.

The MPL 1204 also provides inserts for each of its four buses—appropriately
enough, these are called bus inserts. These allow you to process a group of
signals simultaneously (such as a drum submix being sent to a single track of a
tape recorder) at unity gain. Because they provide a unity gain input and output,
bus inserts can also be used to link multiple MPL 1204s or to bring the output
from another mixer into the MPL 1204 without taking up channel line inputs.
See the “Linking the MPL 1204 With Other Mixers” Application on page 26 in this
manual for more information.

All MPL 1204 insert jacks accept 1/4" TRS plugs, with the ring carrying the send
signal and the tip carrying the return signal; this will normally be connected to a
Y-cord (see the “Connecting The MPL 1204” section on page 12 in this manual
for a wiring diagram). This configuration is sometimes known as an “effects
loop,” since the signal is sent and returned over the same cable.

If nothing is plugged into the channel or bus insert jacks, they have no effect—
but if you connect them to a passive device like a patchbay, you’ll need to
normal (permanently connect) or half-normal (connection is made unless
overriden by a patch cord) the send to the return. Channel insert signals are
returned just before channel Level controls, and Bus insert signals are returned
just before the Bus faders. For this reason, you’ll have to be careful to set the
output of external devices connected this way to unity gain.

12 11 10 9 8 7 6 5 4 123

CHANNEL INSERTS TIP RETURN -RING SEND -SLEEVE GND

4123

BUS INSERTS

UNBALANCED 75Ω +4dBu

MIXER LINKING

24

PFL/AFL Soloing

The MPL 1204 provides two options for soloing input signals in headphones
connected to the front panel headphone jack—Pre Fade Listen (PFL) and
After-Fade Listen (AFL). The Solo switch in the main section (#8 on page 7)
allows you to choose between these two modes of operation. Although they
may at first glance appear similar (and although both are non-mix-destructive),
there is in fact a significant difference between the two.

The main function of PFL is to allow you to check that a signal is actually arriving
at a particular input. When the MPL 1204 is in PFL mode and a channel Solo
switch is pressed in, the pre-fader (but post-eq) signal of that channel alone is
routed to the headphone output. The Bus outputs, Main outputs, and Control
Room outputs are

not interrupted during a PFL solo, so you can press any
channel Solo switch even during recording or live performance without affecting
the main signal flow. This also makes it possible for you to correctly cue up a
tape or CD before bringing it into the main mix (tape or CD players connected to
the MPL 1204’s rear panel Tape/CD input jacks can be routed to channels
11 and 12 by pressing in the main section “Tape” switch).

The main drawback to using PFL mode, however, is that it does not allow you to
hear a signal

in context. Because the PFL soloed signal is monitored pre-fader,
it may sound considerably louder or softer than it actually is in the overall mix,
depending upon the current position of the channel Level control.

Therefore, you may in some circumstances prefer to use AFL mode, which
provides post-fade (and post-eq) soloing. When the MPL 1204 is in AFL mode
and a channel Solo switch is pressed in, the post-fader, post-EQ signal of
that channel alone is routed to the headphone output. Like PFL, AFL is
non-destructive to your mix—the Bus outputs, Main outputs, and Control Room
outputs are

not interrupted during an AFL solo. However, over the headphones,

you’ll hear the AFL soloed signal at its current level.
LEDs in the meter section allow you to see at a glance which mode the

MPL 1204 is in. The leftmost LED (labeled “PFL”) lights steadily red when the
mixer is in PFL mode, while the center left LED (labeled “AFL”) lights steadily red
when the mixer is in AFL mode. In both PFL and AFL modes, you’ll hear the
soloed channel with its EQ settings and all effects being applied and returned via
the channel insert. Note that headphone monitoring in the MPL 1204 is mono
only (channel Pan controls have no effect) and that, since Aux returns cannot be
soloed, they cannot be monitored over headphones.

SOLO

PFL

AFL

SOLO

ON OFF

25

Applications

Here are four suggested applications for the MPL 1204; bear in mind that your particular circumstance may dictate
changes in these suggested signal connections and routings.

Application 1 - Using The MPL 1204 As A Recording Mixer

The MPL 1204 is optimized for use as a recording mixer with multitrack digital or analog recorders. As shown in the
illustration below, microphones and line level signals are connected to various channel inputs. Signal processors are
connected to Aux sends and returns and to channel inserts as required, with Aux send 1 (which is pre-fader) driving a
headphone amplifier for cue mixes. The Control Room outputs are connected to a power amplifier driving studio
monitors. The Main outputs are connected to the inputs of a two-track or DAT recorder, with the outputs of the two-track
or DAT recorder connected to the MPL 1204 tape inputs. The four Bus outputs are connected to the inputs of a
multitrack recorder, with the multitrack outputs connected to four MPL 1204 channel line inputs. During mixdown, those
channels carrying the multitrack outputs are routed to bus 1/2 (via their channel “Mute 3/4” switches), with buses 1 and 2
routed to the Main L/R outputs (by pressing in their Bus “L/R” switches). To listen back to the mix, the channels carrying
the two-track outputs (channels 11 and 12) are routed to bus 3/4 (via their channel “Mute 3/4” switch); then connect
buses 3 and 4 to the Control Room outputs by pressing in their Bus “L/R” switches.

MIDI KEYBOARD

MIDI TONE GENERATOR

R

L

CASSETTE or DAT

FUSE

1A/250V[115V]

0.5A/250V[230V]

R

L

SIGNAL PROCESSOR

MPL 1204 12 CHANNEL MIC MIXER

TRS

STEREO INPUT

POWER

~AC INPUT

115V/230V

50/60Hz, 25W

ON

OFF

DO NOT EXPOSE THIS EQUIPMENT

TIP = LEFT
RING = RIGHT
SLEEVE = COM

TRS

BALANCED
TIP = HI
RING = LO
SLEEVE = COM

TRS INSERT
UNBALANCED
TIP = RETURN
RING = SEND
SLEEVE = COM

XLR

BALANCED

3 = LO
2 = HI
1 = COM

AVIS;

RISQUE DE CHOC ELECTRIQUE

NE PAS OUVRIR

TO RAIN OR MOISTURE.

POWER

115V/230 - 50/60 Hz 25W

RATING

CAUTION

RISK OF ELECTRIC SHOCK

DO NOT OPEN

2

1

3

12

!

DRUM MACHINE

L

R

2

AUX RETURNS
STEREO INPUTS

UNBALANCED 10KΩ +4dBu

2

UNBALANCED <75Ω +4dBu

S / N

2

3

11

AUX SENDS

1

2

1/23/4

1

RIGHT

2

3

BALANCED <75Ω +4dBu

2

2

2

2

1

1

3

10987654321

UNBALANCED
10KΩ -10dBu

L/11

R/12

1

1

3

TAPE IN

12121111101099887766554

LEFT

2

1

3

MAIN

1

3

3

MICROPHONE INPUTS BALANCED +4dBu TO -50dBu

CHANNEL INSERTS TIP RETURN -RING SEND -SLEEVE GND

RIGHT LEFT

CONTROL ROOM

BALANCED <75Ω +4dBu

LINE INPUTS BALANCED +24dBu TO -30dBu

4123

UNBALANCED 75Ω +4dBu

1

3

BUS OUTPUTS

2

1

1

3

3

2

1

3

4

4123

UNBALANCED 75Ω +4dBu

SAMSON

2

1

3

3

BUS INSERTS

MIXER LINKING

2

1

3

11223

Ring

SIGNAL PROCESSOR

-15db

+15db

0

-15db

+15db

0

Tip

SAMSON

+15db

-15db

0

-15db

+15db

0

MULTITRACK

HEADPHONE AMP

SAMSON

S

E

R

V

O

-

2

4

0

26

Application 2 - Using The MPL 1204 As A Main Live Mixer

Here, the MPL 1204’s Main output is connected to the input of a power amplifier, and, from there, to PA speakers.
Microphones and line level signals are connected to various channel inputs, and a two-track tape deck is connected to
the Tape/CD inputs. A submix from Aux send 1 (which is pre-fade) is connected to the input of a second power amplifier
driving onstage monitor speakers so that performers can receive a monitor mix independent of the house mix. Signal is
being sent to an external signal processor via Aux send 2, with a stereo return from that processor is connected to
Aux return 1/2. Another signal processor is connected to channel insert 1 so as to affect the signal coming from the mic
connected to channel 1, and a third signal processor is connected to Bus insert 4 so that a submix of all channels routed
to bus 4 are processed simultaneously.

MIDI KEYBOARD

L

R

DRUM MACHINE

MIDI TONE GENERATOR

CASSETTE or DAT

+15db

0

-15db

0

+15db

-15db

-15db

+15db

0

+15db

-15db

0

SAMSON

SIGNAL PROCESSOR

Ring

Tip

SIGNAL PROCESSOR

SERVO - 240

SAMSON

L

R

MPL 1204 12 CHANNEL MIC MIXER

1/23/4

1

AUX RETURNS

STEREO INPUTS

UNBALANCED 10KΩ +4dBu

S / N

AVIS;

RISQUE DE CHOC ELECTRIQUE

NE PAS OUVRIR

DO NOT EXPOSE THIS EQUIPMENT

TO RAIN OR MOISTURE.

ON

OFF

~AC INPUT
115V/230V

50/60Hz, 25W

SAMSON

TRS
STEREO INPUT
TIP = LEFT
RING = RIGHT
SLEEVE = COM

TRS

BALANCED
TIP = HI
RING = LO
SLEEVE = COM

TRS INSERT
UNBALANCED
TIP = RETURN
RING = SEND
SLEEVE = COM

XLR

BALANCED

3 = LO
2 = HI
1 = COM

FUSE

1A/250V[115V]

0.5A/250V[230V]

CAUTION

RISK OF ELECTRIC SHOCK

DO NOT OPEN

!

115V/230 - 50/60 Hz 25W

POWER
RATING

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

2

AUX SENDS

UNBALANCED <75Ω +4dBu

TAPE IN

UNBALANCED
10KΩ -10dBu

12

11

10987654321

12121111101099887766554

4

11223

3

MICROPHONE INPUTS BALANCED +4dBu TO -50dBu

LINE INPUTS BALANCED +24dBu TO -30dBu

CHANNEL INSERTS TIP RETURN -RING SEND -SLEEVE GND

BUS INSERTS

UNBALANCED 75Ω +4dBu

MIXER LINKING

4123

BUS OUTPUTS

UNBALANCED 75Ω +4dBu

4123

CONTROL ROOM

BALANCED <75Ω +4dBu

RIGHT LEFT

1

2

3

1

2

3

MAIN

BALANCED <75Ω +4dBu

POWER

L/11

R/12

RIGHT

LEFT

SIGNAL PROCESSOR

SERVO - 240

SAMSON

L

R

Ring

Tip

R

L

Applications

27

Application 3 - Using The MPL 1204 As A Keyboard Submixer

Here, various keyboards and MIDI tone generators are connected to the channel line inputs of the MPL 1204. Signal
processors are connected to Aux sends and returns and to channel inserts as required. The Main output can then be
routed to a stereo input channel of a live performance or recording mixing console, with the performer having complete
control over the blend of signals being provided to the sound engineer.

MIDI KEYBOARD

MIDI KEYBOARD

L

R

MIDI TONE GENERATOR

L

R

MIDI TONE GENERATOR

SIGNAL PROCESSOR

SIGNAL PROCESSOR

IN

Ring

Tip

L

R

L

R

SAMSON

MPL2242

MPL2242

MPL 1204 12 CHANNEL MIC MIXER

1/23/4

1

AUX RETURNS

STEREO INPUTS

UNBALANCED 10KΩ +4dBu

S / N

AVIS;

RISQUE DE CHOC ELECTRIQUE

NE PAS OUVRIR

DO NOT EXPOSE THIS EQUIPMENT

TO RAIN OR MOISTURE.

ON

OFF

~AC INPUT
115V/230V

50/60Hz, 25W

SAMSON

TRS
STEREO INPUT
TIP = LEFT
RING = RIGHT
SLEEVE = COM

TRS

BALANCED
TIP = HI
RING = LO
SLEEVE = COM

TRS INSERT
UNBALANCED
TIP = RETURN
RING = SEND
SLEEVE = COM

XLR

BALANCED

3 = LO
2 = HI
1 = COM

FUSE

1A/250V[115V]

0.5A/250V[230V]

CAUTION

RISK OF ELECTRIC SHOCK

DO NOT OPEN

!

115V/230 - 50/60 Hz 25W

POWER
RATING

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

2

AUX SENDS

UNBALANCED <75Ω +4dBu

TAPE IN

UNBALANCED

10KΩ -10dBu

12

11

10987654321

12121111101099887766554

4

11223

3

MICROPHONE INPUTS BALANCED +4dBu TO -50dBu

LINE INPUTS BALANCED +24dBu TO -30dBu

CHANNEL INSERTS TIP RETURN -RING SEND -SLEEVE GND

BUS INSERTS

UNBALANCED 75Ω +4dBu

MIXER LINKING

4123

BUS OUTPUTS

UNBALANCED 75Ω +4dBu

4123

CONTROL ROOM

BALANCED <75Ω +4dBu

RIGHT LEFT

1

2

3

1

2

3

MAIN

BALANCED <75Ω +4dBu

POWER

L/11

R/12

RIGHT

LEFT

Applications

Applications

Application 4 - Linking The MPL 1204 With Other Mixers

The provision of four rear-panel Bus inserts makes it easy to link multiple MPL 1204s or to link the MPL 1204 with other
mixers, without the need to use up channel line inputs. As shown in this illustration, simply connect the main output of
another mixer to one or two MPL 1204 Bus inserts (use two for stereo linking). The signal from that mixer will then be
“submixed” into that bus at unity gain; you can then use that bus fader to blend its relative level with that of signal routed
to other MPL 1204 buses.

28

SECONDARY MIXER

SAMSON

MPL2242

MPL2242

SECONDARY MIXER

MPL 1204 12 CHANNEL MIC MIXER

TRS

STEREO INPUT

POWER

TIP = LEFT
RING = RIGHT
SLEEVE = COM

ON

TRS

BALANCED
TIP = HI
RING = LO

OFF

SLEEVE = COM

TRS INSERT
UNBALANCED
TIP = RETURN
RING = SEND
SLEEVE = COM

RISQUE DE CHOC ELECTRIQUE

DO NOT EXPOSE THIS EQUIPMENT

~AC INPUT

115V/230V

50/60Hz, 25W

XLR

BALANCED

3 = LO
2 = HI
1 = COM

AVIS;

NE PAS OUVRIR

TO RAIN OR MOISTURE.

POWER

115V/230 - 50/60 Hz 25W

RATING

RISK OF ELECTRIC SHOCK

FUSE

1A/250V[115V]

0.5A/250V[230V]

CAUTION

DO NOT OPEN

2

1

3

12

2

AUX RETURNS
STEREO INPUTS

UNBALANCED 10KΩ +4dBu

2

UNBALANCED <75Ω +4dBu

S / N

!

2

3

11

AUX SENDS

1

2

1/23/4

1

RIGHT

2

3

BALANCED <75Ω +4dBu

2

2

2

1

1

3

109 8 7654 321

UNBALANCED

10KΩ -10dBu

L/11

R/12

1

MAIN

1

3

3

MICROPHONE INPUTS BALANCED +4dBu TO -50dBu

TAPE IN

12121111101099887766554

LEFT

RIGHT LEFT

2

1

3

CONTROL ROOM

BALANCED <75Ω +4dBu

2

1

1

3

1

3

3

LINE INPUTS BALANCED +24dBu TO -30dBu

CHANNEL INSERTS TIP RETURN -RING SEND -SLEEVE GND

4123

BUS OUTPUTS

UNBALANCED 75Ω +4dBu

SAMSON

2

2

2

1

3

4

3

BUS INSERTS

UNBALANCED 75Ω +4dBu

MIXER LINKING

2

1

1

3

3

11223

MAIN OUT

LR

1

3

4123

MPL 1204 12 CHANNEL MIC MIXER

TRS

STEREO INPUT

POWER

TIP = LEFT
RING = RIGHT
SLEEVE = COM

ON

TRS

BALANCED
TIP = HI
RING = LO

OFF

SLEEVE = COM

TRS INSERT
UNBALANCED
TIP = RETURN
RING = SEND
SLEEVE = COM

RISQUE DE CHOC ELECTRIQUE

DO NOT EXPOSE THIS EQUIPMENT

~AC INPUT

115V/230V

50/60Hz, 25W

XLR

BALANCED

3 = LO
2 = HI
1 = COM

AVIS;

NE PAS OUVRIR

TO RAIN OR MOISTURE.

POWER

115V/230 - 50/60 Hz 25W

RATING

RISK OF ELECTRIC SHOCK

FUSE

1A/250V[115V]

0.5A/250V[230V]

CAUTION

DO NOT OPEN

2

1

3

12

MASTER MIXER

2

11

AUX RETURNS

STEREO INPUTS

UNBALANCED 10KΩ +4dBu

2

AUX SENDS

UNBALANCED <75Ω +4dBu

S / N

!

2

2

1

3

10 9 8 7 6 5 4 3 2 1

1/23/4

L/11

R/12

1

RIGHT

2

3

BALANCED <75Ω +4dBu

2

2

1

1

3

3

TAPE IN

UNBALANCED

12121111101099887766554

10KΩ -10dBu

LEFT

RIGHT LEFT

2

1

1

3

MAIN

CONTROL ROOM

BALANCED <75Ω +4dBu

2

1

1

3

MICROPHONE INPUTS BALANCED +4dBu TO -50dBu

1

3

3

LINE INPUTS BALANCED +24dBu TO -30dBu

CHANNEL INSERTS TIP RETURN -RING SEND -SLEEVE GND

4123

BUS OUTPUTS

UNBALANCED 75Ω +4dBu

2

1

3

SAMSON

2

2

2

1

3

3

BUS INSERTS

UNBALANCED 75Ω +4dBu

MIXER LINKING

2

1

1

3

3

11223

1

3

4

4123

29

Appendix A: Block Diagram

MAIN OUT L

+4dBU

MAIN OUT R

+4dBU

CONTROL ROOM OUT R

CONTROL ROOM OUT L

+4dBU

+4dBU

PHANTOM

SOLO

AFL R

AFL L

PFL R

PFL L

AUX 2

AUX 1

BUS 4

BUS 3

BUS 2

BUS 1

+5V

VOLTAGE

SELECTOR

POWER TRANSFORMER

LED

PHANTOM

AC INPUT

POWER

SWITCH

LED

PHANTOM POWER

110V/230V,80Hz/50Hz

PRE AMP

10 DOT LED METER R

+4dBU

10 DOT LED METER L

INSERT I/O BUS 3

+4dBU

INSERT I/O BUS 4

+4dBU

MUTE

MUTE

HEADPHONE OUT

AUX SEND 2

+4dBU

AUX SEND 1

+4dBU

+5

POWER

LED

AFL

LED

PFL

LED

+48V

BALANCE

OUT BUS 3

+4dBU

OUT BUS 2

+4dBU

OUT BUS 1

+4dBU

FADER

FADER

SUM

SUM

SUM

SUM

FADER

OUT BUS 4

FADERFADERFADERFADERFADERFADERFADERFADER

+4dBU

BALANCE

INSERT I/O BUS 1

+4dBU

INSERT I/O BUS 2

BUS 1

BUS 2

PAN

3 BAND EQ

MIC(CH1-10)

BALANCED

BUS 3

BUS 4

+

LEVEL

TRIM

H.A

-50dBU --- +4dBU

HIGHMID

LOW

AUX 2

LINE (CH1-10)

-30dBU

AUX 1

INSERT (CH1-10)

+4dBU

BUS 1

BUS 3

BUS 2

BUS 4

BUS 1

BUS 3

BUS 2

BUS 1

BUS 2

BUS 3

BUS 4

PFL R

AFL L

AFL R

SOLO ON/OFF

PFL L

AUX 1

AUX 2

PFL R

AFL L

AFL R

SOLO ON/OFF

PFL L

MUTE 1,2 / 3,4

BUS 4

MUTE 1,2 / 3,4

PAN

B+

+

B+

BALANCE

BALANCE

LEVEL

HIGHMID

3 BAND EQ

LOW

TRIM

H.A

MIC(CH11-12)

BALANCED

-50dBU --- +4dBU

LINE (CH11-12

-30dBU

INSERT (CH11-12)

+4dBU

H.A

AUX RETURN 1/2

+4dBU

H.A

AUX RETURN 3/4

H.A

AUX RETURN 3/4

+4dBU

H.A

AUX RETURN 1/2

30

Specifications

Normal Limit

1. Frequency Response (±3 dB)

Mic in to Main out DC ~ 65 kHz 20 Hz - 50 kHz
Mic in to Aux Send DC ~ 65 kHz 20 Hz - 50 kHz
Aux return to Main out DC ~ 160 kHz 20 Hz - 50 kHz
Tape in to Main out DC ~ 65 kHz 20 Hz - 50 kHz

2. Total Harmonic Distortion (20 Hz to 20 kHz, with 30 kHz LPF)
Mic in to Main out (Trim max) 0.06% < 0.1 %
Line in to Main out (Trim min) 0.009% < 0.03 %
Aux return to Main out 0.07% < 0.03 %

3. Signal to Noise Ratio (30 kHz LPF)
Mic in to Main out (Trim max) 87 dB 82 dB
Mic in to Main out (Trim min) 70 dB 65 dB

4. Maximum Voltage Gain (Trim min/max)
Mic in to Channel insert 0 / 54 dB
Mic in to Bus insert 10 / 64 dB
Mic in to Bus out 20 / 74 dB
Mic in to Main out / Control Room out 30 / 84 dB
Mic in to Aux send 1 10 / 64 dB
Mic in to Aux send 2 20 / 74 dB
Line in to Main out 10 / 64 dB
Aux return to Main out 30 dB
Tape in to Main out 44 dB

5. Residual Noise (with 30 kHz LPF, EQ center, Trim min)
Main min -97.5 dBu
Main max, Bus Fader min -80.0 dBu
Main max, Bus Fader min, all channel VR min -62.0 dBu
Main max, Bus Fader min, all channel VR max -52.0 dBu

6. Equalizer

High (10 kHz) ± 12dB ± 15 dB
Mid (1 kHz) ± 12 dB
Low (100 Hz) ± 12 dB ± 15 dB

7. Crosstalk (@1 kHz, with EQ center)

Channel vs. Channel 85 dB 80 dB
Input vs. Output 85 dB 80 dB

8. Headphone Output (@ 600 ohm, 1 kHz)

100 mW 120 mW

9. Dimensions 19 in (w) x 7.1 (d) x 7 (h)

482 mm (w) x 179 (d) x 177 (h)

10. Weight 15.9 lbs • 7.2 kg

11. AC Power 115 Vac • 60 Hz for UL and CSA version

230 Vac • 50/60 Hz for BSI and Central Europe version

100 Vac • 50/60 Hz for Japan version

Produced by On The Right Wavelength for Samson Technologies Corp.

Copyright 1997, Samson Technologies Corp.

Printed March 1997

Samson Technologies Corp.
575 Underhill Blvd.
P.O. Box 9031
Syosset, NY 11791-9031
Phone: 1-800-3-SAMSON (1-800-372-6766)
Fax: [phone]